Biomechanics of osteoporotic bone

The health problem most commonly associated with osteoporosis is bone fracture, and the feature that distinguishes osteoporosis-related fractures from others is that they generally occur with minimal or no trauma. The sites where most fractures occur are the spine, the hip, and the wrist. In the spine, crushing of the vertebrae, experienced while performing everyday activities, results in an increased kyphosis and loss of height, seen externally in the classical “Dowager’s hump.” Wrist (Colles’ fracture) and hip fractures commonly follow a fall from standing. The mechanics of these fractures, which are determined by the magnitude and location of the force applied to the bone, are discussed elsewhere. Clearly, the strength of the bone is an important factor in whether it will sustain a fracture under a given set of forces. This strength is determined by geometric factors, the size, shape, and internal structure of the bone itself, as well as material factors, such as its composition. In cancellous bone the distinction between material and structure is not always easy to define and treating it as a cellular material has met with a considerable degree of success.^1,2.